How to use online Tcl/Tk documentation

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I cannot figure out how to find, or apply what I have found,
regarding Python/Tcl/Tk tools.  I have successfully installed
Python, Tk/Tcl and PIL on a Win 98 platform, and gotten the
Thumbnail demo working.  I am now trying to adapt it to an
application in imaging of 640 x 480 BMP files.
  My problem is identifying what, and how, to apply tools.
The Tk Library Procedures contain "Tk_GeometryRequest," but
I cannot figure out how to incorporate it in the program.
A skeleton of my context is:
import os
import Image
import ImageTk
import Tkinter
if __name__ == '__main__':
    import sys
    import string

    root=Tkinter.Tk()
    root.title(os.path.basename(sys.argv[0]))
...
I have tried 
    root.Tk_GeometryRequest(...
and
    Tk_GeometryRequest(root,...
and several other seemingly-plausible variations.
All draw opaque diagnostics.
  Can anyone either (1) explain how to correctly
call Tk_GeometryRequest in this environment, or
(2) explain how else to preset the size of the 
main window.  It comes up considerably smaller
than the image I want to display, and I'm trying
to make it simple for users.
  More generally, how does one create the context
in which Tk Library Procedures can be used, and
how does one find documentation for Class Methods
(in C++ terminology) for "names" that can be
found via "dir()"?